Diabetic nephropathy is associated with increased morbidity and mortality, mainly from cardiovascular disease. Although past clinical studies have provided convincing evidence that interruption of the renin angiotensin system (RAS) through the use of angiotensin-converting enzyme (ACE) inhibitors improves the renal outcome in both type I and II diabetes mellitus, the effects of this system on early changes in diabetic nephropathy are not well known. Angiotensin II (Ang II) subtype-1 (AT1) receptors are localized in the renal blood vessels, glomeruli and tubules. AT1 receptor stimulation decreases renal hemodynamic and tubular functions and releases several growth, cytokine and vasoactive factors that enhances many pathologic changes seen in diabetic renal disease. Ang II subtype-2 (AT2) receptors have recently been detected in adult rat kidney glomeruli, blood vessels and tubules. In contrast to AT1 receptors, AT2 receptors stimulation lead to vasodilation, inhibition of cell growth and apoptosis. Our preliminary studies suggest that in early stage diabetic nephropathy, AT2 receptor expression and activity are decreased. This proposal will evaluate the hypothesis that in early stage diabetic nephropathy, the decrease in the AT2 receptor expression and activity contributes to development of this renal disease through increased renal production of tumor necrosis factor-alpha (TNFalpha), transforming growth factor-beta1 (TGFbeta1, endothelin-1 (ET-1) and thromboxan-B2. The proposed specific aims are: AIM I: To test the hypothesis that AT2 receptor inhibits renal production of TNFalpha, TGFbeta1, ET-l and TXB2. AIM II: To test the hypothesis that the decrease in AT2 receptor expression and activity reciprocally increases the AT1 receptor activity to increase renal production of TNFalpha, TGFbeta1, ET-1 and TXB2 in early stage diabetic nephropathy. AIM III: To test the hypothesis that in early stage diabetic nephropathy improving the AT2 receptor expression and activity reduces renal production of TGFbeta1, TNFalpha, ET-1 and TXB2, a process that can prevent the progression of this disease. The proposed studies will help understand the mechanisms that are involved in diabetic nephropathy and could lead to the development of new therapeutic modalities to prevent or slowdown the development of this disease.